1. Field of the Invention
The present invention relates to digital cameras, and more particularly to a digital camera which compresses photographic image data according to a JPEG format and records the compressed data on a recording medium such as a flash memory.
2. Description of the Related Art
In a conventional digital camera, the photographic image data is temporarily stored within a memory such as a DRAM. This image data is compressed block by block. When compression of all the blocks is completed the compressed data is then recorded on a recording medium.
In such a digital camera, however, the compressed data must be once stored in a work area of the DRAM. This, accordingly, has resulted in a problem that the capacity of the DRAM increases as the CCD increases in the number of pixels.
Meanwhile, Japanese Patent Laying-open No. H10-145716 laid open on May 29, 1998 discloses a technology wherein the compressed data is once stored within a vacant area of a frame memory and thereafter rewritten onto a flash memory. However, this method utilizing a vacant area as a buffer memory still requires a memory capacity to offer a vacant area to be secured.
It is therefore a primary object of the present invention to provide a digital camera which is capable of decreasing a required memory capacity.
According to the present invention, a digital camera comprises: a memory having at least an image data area; an image taking means for taking a photographic subject image and outputting first image data having a predetermined number of frames; a first writing means for writing the first image data to the image data area; a compressing means for compressing the first image data by a predetermined amount; an overwriting means for writing compressed data outputted from the compressing means over the image data area; and a recording means for recording the compressed data written on the image data area into a recording medium.
If the predetermined number of frames of the first image data is outputted from the image taking means, the first writing means writes the outputted first image data to the image data area formed in the memory. The compressing means compresses, in the predetermined amount; the first image data written on the image data area. The compressed data thus obtained is written over the image data area by an overwriting means. If the compressed data is stored in the image data area, the recording means records this compressed data onto the recording medium. It is possible to reduce the memory capacity by writing the compressed data over the image data area by the overwriting means.
In a certain aspect of the present invention, the overwriting means writes the compressed data to the image data area in a manner avoiding the first image data unprocessed by the compressing means.
In another aspect of the present invention, the memory further possesses a first work area, and the compressing means including a data processing means to perform a predetermined process on the first image data to create a second image data, a storing means to store the second image data in the first work area, a first reading means to read the second image data in the predetermined amount out of the first work area, and ,a data compressing means to compress the predetermined amount of the second image data. As a result, compressed data is obtained.
In one embodiment of the present invention, the data compressing means compresses the second image data according to a JPEG format. In another embodiment of the present invention, the first image data has color components different on a pixel-by-pixel basis, and the predetermined data process including YUV conversion. In another embodiment of the present invention, a thumbnail creating means creates thumbnail image data from the second image data, wherein the recording means records the compressed data together with the thumbnail image data into the recording medium. Incidentally, the memory further possesses a second work area, and the thumbnail creating means creating the thumbnail image data using the second work area.
In still another aspect of the present invention, the first image data is interlace scan data, and the first writing means writing odd field data and even field data separately into the image data area.
In another aspect of the present invention, if a particular mode is set, a disabling means disables the overwriting means and an enabling means enables a forming means and a third writing means, thereupon, a compression data area is formed in the memory by the forming means, and the compressed-data outputted from the compressing means is written to the compression data area by the third writing means. The recording means records the compressed data written in the data area to the memory medium.